Automatic electronic timing device



July 5, 1949.- s. s. HATFIELD 2,474,341

AUTOMATIC ELECTRONIC TIMING DEVICE mea Aug. 2s, 194s All ` 55756 T/ME@ INVENTOR. I waa J. Mr/75m BY Mia-glia Patented July 5, 1949 Claims:

l Thet invention :described herein may be manufactured and fusedfbyf or for the.' Government7 for governmental purposes Without" payment to me oilany royaltythereon.

'IhiSPinVentiOnVreIates to automatic electronic timingdevicesw- Conventio'nal'A means for opening: and closing thelbombbay doors vcfa-'bombing aircraft re;- quriresrtheil use'f'ofan electric motor' driven crank. 'l'liis'y means for-opening and-'closing bomb bay doorsrequiresathe bombardier to open the bomb bay'doors before rthewbombrun-is started. The act oflopenin'g the bombl bayl doors so far in advance'of actual-fly -releasingthe bombs, signals to enemy anti-aircraft gunners that such bomb` ruri isabout to begin. .Since itis'well understood in the artthat While onf-such bomb run; the bombi ing aircraft-'must Amaintain an unswer'ving course; enemy gunnerscani, in view of the premature -disclosure that=the bomb'er is about'to begin its bomb run,' more' accurately concentrate their fire.

Iri an effort to overcome theproblem-present*- ed'by- 'opening the-bomb bay doors when the bomb runbegins;-'the'pop open door method was con ceiv'ed." I-Idvvever,l no method Was heretofore available for l supplying thec correct"desired lapse oftime afterthe door'lopening mechanism was actuated by-the bomb sight for opening the bomb bay-z doors", 'and the actual'bomb releaser time, the release ofthe bombs being desired as` immedi'i ately after `thefbo'mb"bay doors are completely opened as: possible'.- Since', therefore, the usual time for popping open the bomb bay doors re-V quires one' to `one' and onehhalf seconds, depend-y ing uponthe type-offaircraft'and the'type of door opening mechanism, a predeterminedl time inter` Val, approximately two seconds, isnecessary from the time 'that' the `dooropening mechanism is triggered-- by the'- bomb* sight, and actual bomb release, to insure ythe bomb bay doors being come* pleteflyf'op'ened before' 'releasing the bombs". This predetermined time interval yis setup in the bomb sight controls `in such a manner' that the triggerr ingimpulse'from'` the bomb sight to the door open'-I ing mechanism'occurs by thispredetermined'in`- te'rvalof time before'th'e desiredfbomb release point. Other problems which have heretofore not b'enisolved are loss of accuracy in the timing ,device due to' supply voltage fluctuations and lur-` 'midityg 'the limitation on-*the size of components Whi'ch'may ibci-"carried in an aircraft, andv the requirement 'that a timing device' for releasing bombs-a vpredetermin-ed periodi-'of time after the bomb-bay doorsw-arefopeneur'and closing bomb doorsrfraitpredeterminedcperiodof tim'ea'after therlastbomb has beexrreleased,v operate with ex; tremehaccuracy'lutilizing ,the 10W voltage supply generatediiby-'Jthe aircrafts power supply.'v Vari'-v ous 'other characteristics: must 'be achieved vin lor; derzth'at thisiftimirig'zdevicefshall be satisfactory fromfrthf. standpoint 'ofwsta'bilityand accuracy ofloperation and shall be'commercially feasible in its. construction; as will be-more apparent hereafter;-

It is; threiioirefamobject of this invention to providef"circuitiA means: fozfpermitting l'extremely accurate'timingf intervals at any availablesupply voltagfa.

Anotherobj'ect iis-to' provi-'dei accurate timing in-4 tervalsunden conditions: limiting. the size of availab-ler'component's and:requiringy utilization 'of the low voltage supply ffroman aircraft generator.

Aifurthenobject iszto providecmeans for achievingracourate timing intervals for releasing bombs invia bomber.'-ail-craft'when' used in combination Witlia bomb sight and anintervalometerfinfa bombing system'zf Arstill4 furtherobjectis to provide circuit means for:automatical1y,felectrically releasing .bombs` at a predetermined period: of. time;

Other: objectsvand features of' novelty -will f be apparentlfrom'the.following `description and the annexedfudrawings', -itlibe'in'g- 'clearly understood; howeverttha'tthe:inventionvis not limited in any Wayfby'sucir-description andi-drawings or other- Wise than byfthlappended claims.

Referring now' to the drawings in which similar'reference ni-imerals"refer` to like parts:

Fig. 1 is .a `b1ocir-niagram illustrating the interconneotionooithe components of this invention with foth'eri struc-tural elements of a bombing systemb'andil Fig. -2 .isa'circuitldi'agraml ofa complete bomb-l ing systempartially schematic, embodying the present mventioni' Referring nowf-more particularly to Fig. 1v of the drawingsefthere isfshotvniin-..bl'oekform a bom-b;` ingvsyst'em' embodying'a-'pr'eferred form of the presenti invention; 11n general, a Asystem includes aibomb' sighti Illlwhichlisponnected to and si' multaneouslmactuatesa bomb` 'release timer' I I', forming'fpart; of'ftimingndevice I 2',` and a door opening mechanism' 'I 3i; for'lopening the bomb bay doors-53 inf-a"bomber"aircraft and delaying the dropping'of: tlrelbombsffor a predetermined period of-tim'e -a-ttei` the bombi bay doorscommence to openlfthis delay'beingisufcient to permit the bomb bay--cd'obrsIJ-torrbecompletely 'opened before tha-bombs are.'relea'se'd` The-bomb sight I0 may beinfiany. preferred-typen long fasf provision is made therein for closing contacts or otherwise producing an electrical signal at the instant of bomb release and so long as the sight is of such a type that provision may be made for setting ahead the time when the contacts close, or when the electrical signal is given, in order to take care of the time-delay produced by the bomb release timer II. In the Norden type of bomb sight, an electrical signal is produced by the sight when the aircraft arrives at the proper position for the bombs to hit the target. In this type of sight, the 2-second time-delay provided by the timer II may be compensated for by adding two seconds to the time of fall when this data is converted into disc speed which is then set into the sight. This will cause the electrical impulse produced by the sight to occur two seconds prior to the proper time of release of the bombs for hitting the target and thereby compensate for the 2-second delay occurring in timer II. Alternatively, a bomb sight structure such as that shown in the patent to Inglis, No. 2,105,147, filed January 11, 1938, may be used for compensating for the 2-second time-delay interval. As shown in Fig. 19 of this patent, when the switch 164 is in the position shown in solid lines in the figure, the solenoid 165 will be energized when contacts 151, 156 meet. The solenoid 165 in turn may be arranged to trip any suitable type of a bomb release mechanism. The contacts 151, 155 are the ones normally used in order to cause the bomb to strike the target when the proper constants have been set into the sight. However, by throwing the switch 164 to the dotted line position shown in Fig. 19, the solenoid 165 may be actuated prior to the proper time of release as determined by the contacts 151, 156. With the switch 164 in the dotted line position, the control of the solenoid 165 is switched over to contacts 152, 157 which make contact somewhat earlier than contacts 151, 156. By adjusting contact 157 so that this contact engages contact 152 two seconds ahead of the time when contacts 151, 156 meet, the 2-second time-delay provided by the bomb release timer II may be compensated for and the bomb or bombs will be released irom the aircraft at the same instant that contacts 151, 156 engage with one another.

Bomb release timer I i activates an intervalometer i4 oi the type described in the copending application of Habig, Ser No. 494,027, filed July 9, 1943, now Patent No. 2,388,686, for triggering a bomb rack i5 to drop a plurality of bombs in a predetermined timed sequence. While intervaloineter i4 is operating, each succeeding bomb release triggers bomb bay door closing timer I6, forming the other part of timing device I 2. Howcver, since the time interval between each bomb release is much less than the time required for actually causing door closing timer I6 to operate only after the last bomb is released does the door closing timer I5 actually operate to delay operation of the door closing mechanism Il for a predetermined period of time after the last bomb is dropped, so as to permit the last bomb released to completely clear the bomb bay doors.

Referring now to Fig. 2 of the drawings, the reference numeral Il! represents a bomb sight which is nre-set by the bombardier of a bombing aircraft to trigger the door opening mechanism, for popping open the bomb bay doors 53 at a predetermined time during the bomb run and simultaneously energizing relay coil I8 which corresponds to relay coil |65 of Fig. 19 in the patent to Inglis, and which operates to close relay contacts I9 and 20 and open contact 2I. The door opening mechanism for popping open the bomb bay doors 53 comprises a hydraulic actuating mechanism consisting of solenoid 54 connected to bomb sight I0 and solenoid 54a connected to relay contact 41 which solenoids actuate pilot valve 55 for controlling the flow of hydraulic iluid into either end of servo cylinder 5I, depending on whether solenoid 54 or solenoid 54a is energized. Servo cylinder 5I drives piston rod 52a which actuates linkages 52 operably connected to bomb bay doors 53. In deenergized condition of relay coil I3, grid electrode 25 of triode tube 22 and the grid side of capacitor 26 are connected to ground. The cathode side of capacitor 26 is connected to the power supply through resistor 21. Resistor 21 is of such value as to permit rapid charging of capacitor 26 but does not place an appreciable drain on the power supply when contact 26 is closed. In this deenergized condition of relay coil I8, tube 22 is nonconducting since its cathode 23 is at the same potential as its plate 24. When relay coil I8 is energized by bomb sight Ill closing contacts I9 and 2t it remains locked in energized condition since the relay armature associated with contact I9 is connected directly to the power supply through contact 39 of relay coil 36 thus locking contact 29 in closed position. Closing contact 2t connects cathode 23 of tube 22 and the cathode side of capacitor 26 to ground thereby placing the positive cathode side of capacitor 26 at ground potential and disconnecting the grid side of capacitor 25 and grid electrode from ground. Disconnecting the grid side of capacitor 26 and grid 25 from ground places both grid 25 and the grid side of capacitor 26 at negative potential by the amount of the voltage across capacitor 25 which is substantially equal to that of the power supply 28. The capacitor 2S immediately starts to discharge through the power supply and resistors 29 and 30, thus allowing the potential of grid 25 to rise until the cut-off point of tube 22 is reached, at which time the tube begins to conduct. The resulting current ow through relay coil 3l causes the relay to operate to close contact 32 and initiate operation of intervalometer I4. The time-delay interval before actuation of intervalometer I4 is controlled by the values of the resistance-capacitance network consisting of resistors 29 and 36 and capacitor 2S. This interval may be adjusted by changing the value of variable resistor 30. Each release impulse from intervalometer I4 sequentially energizes relay coil 33 closing contacts 34 and 35. When contact 34 is closed, relay coil 36 is energized, closing contacts 31 and 38 and opening contact 39. When relay coil 3E is energized, it remains locked in energized condition since the relay armature associated with contact 37 is connected directly to the power supply through contact 48 of relay coil 46, locking contact 38 in closed position. The opening of contact 39 deenergizes relay coil I8 opening contacts I9 and 25, causing tube 22 to return to its nonconducting state. Contact 35, when closed by energization of relay coil 33 by intervalometer I4, connects the grid 42 oi tube 4I and the grid side of capacitor (i9 to ground. This capacitor is in a charged condition with the grid side positive, having previously charged through resistor 45; however, the charge will be small because any appreciable build-up of voltage across capacitor 43 is prevented by the conductance of the grid-cathode path of tube 4I. When contact 35 closes, condenser 43 discharges through the power supply and resistor 44 and then charges, with reversed polarity, to a potential substantially equal to that of the power supply. This charging must progress rapidly enough for the negative grid potential to exceed the cutofi value before contact 38 closes and plate potential is applied to tube l i, in order to avoid premature energzation of relay coil 46. Deenergization of coil 33 causes lower contact 35 to open and the upper contact to make, thus connecting the cathode side of condenser 43 to ground. The condenser then discharges through the power supply and resistor 45, causing the potential of grid 42 to rise or become less negative with respect to the cathode. However, before the grid potential reaches the cut-off point, coil 33 is again energized by the intervalometer, thus closing contact 35 and causing condenser 43 to repidly recharge through resistor M. In other words, the time interval between each bomb release impulse from intervalometer i4 is shorter than the time required for condenser 43 to discharge sufiiciently to allow tube 4| to become conducting. After the last bomb is released, however, the coil 33 remains deenergized and contact 35 is open for a sufficient length of time to allow condenser 43 to continue its discharge until the potential of grid 42 has risen to the cut-off point, at which time tube 4I becomes conducting. The plate current of tube 4l in its conducting state energizes relay coil 46 closing contact 41 and opening contact 48. Closing contact 41, energizes solenoid 54a for closing bomb bay doors 53 and opening Contact 48 deenergizes relay coil 36 opening contact 38. Opening of contact 38 deenergizes plate 40 of the tube 4I thereby causing the tube to become nonconducting. Capacitor #i9 is connected between the power supply end of relay coil 46 and ground, and maintains relay coil 46 in an energized condition long enough to enable contact 4l to energize solenoid 54a to cause complete closing of the bomb bay doors.

Pilot light 5!) is connected between the filament lead of tube 4i and ground to indicate to the bombardier the fact that the filaments of tubes 22 and 4| are lighted. Since the filaments of tubes 22 and 4| are connected in series with one another, the lighting of pilot light 59 indicates that the filaments of the tubes are intact and that the cathodes are being heated thereby.

Having thus described my invention, I claim:

1. A bomb control system for bombing aircraft comprising a bomb sight of the type capable of producing an electrical signal preceding the proper instant of bomb release by a predetermined time interval, a set of bomb bay doors, electrically controlled actuating means for said doors, means for applying said bomb-sight signal to said actuating means for opening said doors at the occurrence of said signal, a first delay means for producing a first delay period, means for applying said bomb-sight signal to said first delay means for initiating operation thereof, an intervalometer capable of responding to the application of an electrical signal thereto to produce a fixed number of successive electrical release signals having equal time separation, means connected between said first delay means and said intervalometer for initiating operation of the latter at the end of said first delay period, a bomb rack of the type actuated by an electrical signal to effect bomb release, means connected between said intervalometer and said bomb rack to apply said release signals to said bomb rack, a second delay means for producing a second delay period exceeding the time interval between the successive release signals produced by said intervalometer, means for applying each of said release signals to said second delay means for initiating operation thereof, and means connected between said second delay means and said bomb bay door actuating means for closing said bomb bay doors at the end of said second delay period.

2. Apparatus as claimed in claim 1 in which said first delay means comprises a first condenser, means providing resistive charging and discharging circuits for said first condenser, a first vacuum tube having its grid and cathode connected to the negative and positive terminals respectively of said rst condenser when in its charged condition, and means normally connecting said first condenser in its charging circuit and actuated by said bomb-sight signal to connect said first condenser in its discharging circuit; and in which said means for initiating operation of said intervalometer comprises a current responsive means located in the anode circuit of said first vacuum tube for applying a voltage to said intervalometer when the anode current of said first tube reaches a certain value.

3. Apparatus as claimed in claim 2 in which said second delay means comprises a second condenser, means providing resistive charging and discharging circuits for said second condenser, a second vacuum tube having its grid and cathode connected respectively to the negative and positive terminals of said condenser when in its charged condition, and means normally connecting said second condenser in its discharging circuit and actuated by the release signals from said intervalometer to connect said second condenser in its charging circuit; and in which said means for closing said bomb bay doors comprises a current responsive device in the anode circuit of said second tube for applying a voltage to said electrically controlled door actuating means for closing said doors when the anode current of said second tube reaches a certain value.

4. Apparatus as claimed in claim 3 in which means are provided for holding said means for connecting said first condenser in its discharging circuit, in its actuated condition until the occurrence of the first release signal produced by said intervalometer.

5. Apparatus as claimed in claim 4 in which means actuated by said first release signal from said intervalometer are provided for connecting a source of direct current in the anode circuit of said second vacuum tube, and in which means operated by said current responsive device in the anode circuit of said second tube is provided .for disconnecting said source of voltage from said anode circuit upon operation of said current responsive device.

SAMUEL S. HATFIELD.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,145,042 Dimond Jan. 24, 1939 2,269,603 Rockwood, Jr. Jan. 13, 1942 2,363,750 Schmuecl Nov. 28, 1944 2,373,247 Jones Apr. 10, 1945 2,378,259 Towner June 12, 1945 

